Improve #917 not to rely on #toString() method behavior (#921)

Author: seratch

slack-api-client/src/main/java/com/slack/api/audit/impl/ThreadPools.java

@@ -22,7 +22,7 @@ public static ExecutorService getDefault(AuditConfig config) {
     }
 
     public static ExecutorService getOrCreate(AuditConfig config, String enterpriseId) {
-        String providerInstanceId = config.getExecutorServiceProvider().toString();
+        String providerInstanceId = config.getExecutorServiceProvider().getInstanceId();
         Integer orgCustomPoolSize = enterpriseId != null ? config.getCustomThreadPoolSizes().get(enterpriseId) : null;
         if (orgCustomPoolSize != null) {
             return ENTERPRISE_CUSTOM

slack-api-client/src/main/java/com/slack/api/methods/impl/ThreadPools.java

@@ -21,7 +21,7 @@ public static ExecutorService getDefault(MethodsConfig config) {
     }
 
     public static ExecutorService getOrCreate(MethodsConfig config, String teamId) {
-        String providerInstanceId = config.getExecutorServiceProvider().toString();
+        String providerInstanceId = config.getExecutorServiceProvider().getInstanceId();
         Integer teamCustomPoolSize = teamId != null ? config.getCustomThreadPoolSizes().get(teamId) : null;
         if (teamCustomPoolSize != null) {
             return TEAM_CUSTOM

slack-api-client/src/main/java/com/slack/api/scim/impl/ThreadPools.java

@@ -22,7 +22,7 @@ public static ExecutorService getDefault(SCIMConfig config) {
     }
 
     public static ExecutorService getOrCreate(SCIMConfig config, String enterpriseId) {
-        String providerInstanceId = config.getExecutorServiceProvider().toString();
+        String providerInstanceId = config.getExecutorServiceProvider().getInstanceId();
         Integer orgCustomPoolSize = enterpriseId != null ? config.getCustomThreadPoolSizes().get(enterpriseId) : null;
         if (orgCustomPoolSize != null) {
             return ENTERPRISE_CUSTOM

slack-api-model/src/main/java/com/slack/api/util/thread/ExecutorServiceProvider.java

@@ -23,4 +23,15 @@ public interface ExecutorServiceProvider {
      */
     ScheduledExecutorService createThreadScheduledExecutor(String threadGroupName);
 
+    /**
+     * Returns the unique identifier for this instance. The value must be unique among different implementations.
+     * The default implementation is exactly the same with the default #toString() method.
+     * The reason why we have this method is to avoid unexpected side effect
+     * in the case where a developer customizes the #toString() method behavior.
+     * @return an instance ID
+     */
+    default String getInstanceId() {
+        return this.getClass().getName() + "@" + Integer.toHexString(this.hashCode());
+    }
+
 }

slack-api-model/src/test/java/test_locally/util/ExecutorServiceProviderTest.java

@@ -0,0 +1,28 @@
+package test_locally.util;
+
+import com.slack.api.util.thread.ExecutorServiceProvider;
+import org.junit.Test;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.ScheduledExecutorService;
+
+import static org.junit.Assert.assertTrue;
+
+public class ExecutorServiceProviderTest {
+
+    @Test
+    public void getInstanceId() {
+        ExecutorServiceProvider provider = new ExecutorServiceProvider() {
+            @Override
+            public ExecutorService createThreadPoolExecutor(String threadGroupName, int poolSize) {
+                return null;
+            }
+
+            @Override
+            public ScheduledExecutorService createThreadScheduledExecutor(String threadGroupName) {
+                return null;
+            }
+        };
+        assertTrue(provider.getInstanceId().matches("test_locally.util.ExecutorServiceProviderTest\\$1\\@\\w+$"));
+    }
+}